v0.4.0 — Sidebar offcanvas mode

Sidebar offcanvas mode

• PhlexKit::SidebarWrapper.new(collapsible: :offcanvas) — the wrapper becomes the phlex-kit--sidebar Stimulus scope and renders a click-to-close scrim. :none (default) is unchanged.
• New PhlexKit::SidebarTrigger — hamburger toggle (:menu icon, block overrides).
• Desktop: the rail slides out of the layout (data-collapsed, transitioned, reduced-motion aware).
• Mobile (<768px): fixed overlay drawer behind the scrim (data-open); closes on scrim click, Escape, and turbo:before-cache (DOM-only state — Turbo page caches always restore closed).
• New sidebar_controller.js registered via registerPhlexKitControllers; docs example at /docs/sidebar.